The single case report by Hao et al. (1) describing the unique pathological microstructure of a calcified nodule (CN) in an 89-year-old woman dying of congestive heart failure provides unique clues to advance our ability to interpret the images provided by intracoronary diagnostic techniques. The beauty of this report is that a detailed pathological analysis of the CN was combined with corresponding intravascular ultrasound (IVUS), optical coherence tomography (OCT), and coronary angioscopy findings. Of note, this CN was not complicated because it was completely covered by a continuous endothelial layer and had no trace of any residual superficial thrombus. Interestingly, however, the inner aspect of the CN had multiple patchy, irregular, calcified areas, some of which were associated with fibrin deposition and others showing neovascularization. As expected, IVUS depicted a bright protruding mass with marked posterior shadowing, the hallmark of a heavily calcified plaque with this technique. Surprisingly, however, on OCT, a bright protruding mass with an irregular surface causing major dorsal shadowing was detected. This, in turn, constitutes the hallmark of a large “red thrombus” by this technique, as emphasized in all the available consensus documents on OCT (2,3) and some dedicated original reports (4). An adjacent image of classic superficial calcification (a dark area with sharply delineated borders without attenuation) was also demonstrated by OCT, corresponding well with the adjacent calcified plaque (bright echoes with shadow) also disclosed by IVUS (1).

We previously suggested that some CNs may actually induce intense dorsal shadowing that makes the differential diagnosis difficult of this elusive clinical entity (5,6). However, this concept is still not widely accepted (2–4). Furthermore, we have also suggested that a complication on a superficial “nonprotruding” calcified plaque may cause an acute coronary syndrome (5). In this setting, superficial calcification with images suggestive of a protruding red thrombus versus protruding bony calcified spicules may be unraveled by OCT (5). The striking images provided by Hao et al. (1) showing a close correlation between pathological and OCT findings in a human coronary artery are instrumental in demonstrating that uncomplicated CNs may actually present as irregular protruding bright masses inducing major shadowing on OCT. Whether similar OCT findings may be induced by CNs without internal fibrin deposition warrants further investigation (1). Moreover, these pathological findings emphasize that OCT images highly suggestive of a red thrombus may actually emerge from uncomplicated nonculprit lesions. Oftentimes, a single image generates more convincing evidence than large studies or wordy speculative expert discussions. We need to keep learning from the never-ending surprises that are continuously offered in the clinical setting.

(2012) Consensus standards for acquisition, measurement, and reporting of intravascular optical coherence tomography studies: a report from the International Working Group for Intravascular Optical Coherence Tomography Standardization and Validation. J Am Coll Cardiol59:1058–1072.